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. 2016 Mar 11;9(1):13. doi: 10.3390/ph9010013

Figure 4.

Figure 4

ALL-38 is processed from hCAP-18 post-ejaculation. (A) Processing of hCAP-18 to ALL-38 by gastricsin occurs at the optimum pH of 4. Although both hCAP-18 and gastricsin are seminal plasma components, this processing does not occur in the seminal plasma due to its high buffering capacity at neutral pH. (B) Immunoblotting showing that processing of hCAP-18 to ALL-38 can occur in acidified seminal plasma. Anti-LL-37 antibody used in immunoblotting was produced against the whole LL-37 sequence [79] and therefore, it recognized only ALL-38 and hCAP-18, but not cathelin. Before acid treatment (BA), seminal plasma contains hCAP-18 and its oligomers (Oligo; ~60 kDa), as well as a 14 kDa band (presumably a cleaved product of hCAP-18). Upon acidification of seminal plasma with HCl to pH 4, hCAP-18 is processed to ALL-38; this is due to the activation of gastricsin. AA = after acid extraction. (C) ALL-38 is produced 2–6 h post-ejaculation. Upon ejaculation, seminal plasma neutralizes the vaginal pH, and it takes 2–6 h post-ejaculation for the vagina lumen to resume its acidity. Only at this time, ALL-38 is produced from hCAP-18 via gastricsin activity. However, immediately after semen liquefaction (30 min post-coitus), motile sperm in the ejaculate swim into the uterine cavity. Therefore, motile sperm are never exposed to ALL-38. The drawing is based on Sørensen et al. [153].